Thermal shock-resistant clay

ABSTRACT

A CERAMIC STONEWARE OR WHITEWARE (PORCELAIN) MADE OF A THERMAL SHOCK-RESISTANT MIX OF CERTAIN PROPORTIONS OF COARSE AND FINE PARTICLES OF A LITHIUM MINERAL PETALITE OR SPODUMENE, WITH A CLAY; BAL CLAY AND FIRECLAY IN THE CASE OF SOTNERWARE, AND KAOLIN AND PERMISSIBLY BALL CLAY IN THE CASE OF WHITEWARE. SHAPES ARE FIRED AT 1236 TO 1285*C. INCLUSIVE (CONES 8-10).

June 18, 1974 a. M. SMYSER 3,811,763

THERMAL SHOCK-RESISTANT CLAY Filed March 13.. 1972 U.S. Cl. 106-45 5 Claims ABSTRACT OF THE DISCLOSURE A ceramic stoneware or whiteware (porcelain) made of a thermal shock-resistant mix of certain proportions of coarse and fine particles of a lithium mineral petalite or spodumene, with a clay; ball clay and fireclay in the case of stoneware, and kaolin and permissibly ball clay in the case of whiteware. Shapes are fired at 1236 to 1285 C. inclusive (cones 8-10').

DISCLOSURE OF INVENTION This application is a division of my copending United States application Ser. No. 50,109, filed June 26, 1970 for Thermal Shock-Resistant Clay and Process, carrying forward the subject matter of original claims 1 to 9 relating to the thermal shock-resistant clay. Application Ser. No. 50,109 is a continuation-in-part of application Ser. No. 726,296, filed May 3, 1968 for Thermal Shock-Resistant Clay and Process and since abandoned.

' The present invention relates to ceramic stoneware or whiteware (porcelain).

A purpose of the invention is to provide a thermal shock-resistant clay product which is of very low thermal expansion and can withstand tremendous thermal shock.

A further purpose is to brighten glaze on stoneware and whiteware by providing a basic composition which will make the color of the glaze warmer.

A further purpose is to incorporate in a thermal shockresistant stoneware composition of a character which is fired at 1236 to 1285 C. inclusive (cones 23-10), a relatively coarse lithium mineral in the form of 8-25% of petalite or 7-25% of spodumene, the coarse mineral having at least 65% and preferably 80% through 20 and on 200 mesh, a relatively fine lithium mineral of the character of 10-50% of petalite or spodumene, said fine mineral having atleast 80% and preferably at least 90% through 200 mesh, with 20-40% of ball clay and 2030% of fireclay when petalite only is employed, and the quantity of fine lithium mineral exceeds the quantity of coarse lithium mineral, 20-33% of fireclay when only petalite is employed and the quantity of coarse lithium mineral exceeds the quantity of fine lithium mineral, and with 20-32% of fireclay when spodumene is employed as at least one of the components.

A further purpose is to produce a thermal shockresistant clay whiteware (porcelain) composition of a character which is fired at 1236 to 1285 C. inclusive (cones 8-10), by blending togetherarelatively coarse lithium mineral of the character of 8-25%. of petalite and 7-25 of spodumene,.saidcoarse mineral having at United States Patent 0 CC a,

least and preferably at least through 20 and on 200 mesh, a relatively fine lithium mineral of the character of 10-50% of petalite or spodumene, said fine mineral having at least 80% through 20 mesh, with 25- 83% of kaolin and up to 35% of ball clay, the inclusion of ball clay being optional.

Further purposes appear in the specification and in the claims.

The drawings show a flame test procedure used in determining the suitability of the products of the invention.

FIG. 1 is a perspective showing the flame test.

FIG. 2 is an axial section of the flame test shown in FIG. 1.

In the prior art extensive use has been made of lithium aluminum silicates such as petalite and spodumene and they have been known to provide ceramic compositions of low thermal expansion. Beck U.S. Pat. 3,279,930, granted Oct. 18, 1966, for Ceramic Product and its Preparation, provides a ceramic composition containing finely divided spodumene fired at cones 12-16 inclusive.

Beck U.S. Pat. 3,228,779, granted Jan. 11, 1966, for Refractory Products and Method of Making, described a castable refractory composition having colloidal silica.

Genton U.S. Pat. 2,662,028, granted Dec. 8, 1953, for Mill Addition Agent for Enamel Slips relates to an enamel, and Arlett et a1. U.S. Pat. 3,309,208, granted Mar. 14, 1967, for Methods for Controlling the Thermal Expansion Properties of Ceramics, employs a glass frit with a lithium mineral and clay.

Burgess et a]. U.S. Pat. 2,260,000, granted Oct. 21, 1941, is for a Ceramic Composition which incorporates a potash soda-bearing aluminum silicate mineral with spodumene.

Smoke U.S. Pat. 2,726,964, granted Dec. 13, 1955, for Modified Quartz and Method of Making, is a quartz-like ceramic-containing lithium mineral.

McMillan et a1. U.S. Pats. 3,352,656 and 3,352,698, granted Nov. 14, 1967, described glazes containing lithia.

The present invention is concerned with making stoneware and whiteware (porcelain) from clay mixtures which will be suitable for producing dishes, oven 'dishes, crockery, refractories and other heat resistant ceramics of substantially clay base materials.

The products of the invention are fired at 1236 to 1285 C. inclusive (cones 8, 9 or 10),,as is common practice in making stoneware and whiteware.

Unlike many prior art clay base stonewares and whitewares, the composition of the present invention is capable of withstanding high temperature gradients and rapid changes intemperature without cracking or checking.

As shown in the drawing, a test specimen ceramic disc 20 produced according to the invention and suitably fired can receive an impingement of an oxyacetylene flame 22 from a torch 21, at a point 23, for example near the middle, locallizing a very high temperature at that point, say 3000 F., without cracking either in heating, or in cooling when the flame is removed after say five minutes.

Likewise, a container such as a dish made of the composition of the invention and containing ice can be placed in an oven or under, an open flame such as a Bunsen burner or on top of a hot stove without danger of cracking' dueto' the inequality in temperature.

I have discovered also that the stonewares and whitewares produced according to the invention when fired and then coated with conventional glazes and refired are much more effective in brightening the colors of the glazes than prior art stonewares and whitewares. In comparable tests, a Warmer color is obtained from a glaze on the stoneware or whiteware of the invention than on a prior art stoneware or whiteware, the glaze being in every case conventional as well known in the art, such as iron oxide, cobalt carbonate, calcium carbonate and nephleine syenite. A wide variety of other well known glazes is advan tageously used on the stoneware and whiteware of the invention.

The important aspect of the invention is the incorporation in a thermal shock-resistant clay, of a lithium mineral of the class consisting of petalite and spodumene in the form of two different components, one of which is a relatively coarse component and the other of which is a relatively fine component. In the case of making stoneware, the coarse and fine lithium mineral in the proper proportions are blended with ball clay and with fireclay. In the case of whiteware or porcelain, the coarse and fine lithium mineral in the correct proportions are blended with kaolin and optionally with ball clay.

COARSE LITHIUM MINERAL The coarse lithium mineral may be petalite or spodumene. These materials may be used eitherin the raw form or after calcining, for example to a temperature of the order of 450 to 500 C. or higher. A coarse petalite, nominally 20 mesh, and not calcined, may have a typical There is at least 6 5% coarser than 200 mesh. In the case of spodumene of coarse particle size, a typical chemical analysis is as follows:

Chemical: Percent Li- O 7.17 N320 K 0.29 CaO 0.35 MgO trace MnO 0.086 Cr O 0.0004 F203 A1 0 27.06 P 0 0.44 SiO 63.66 TiO 0.05 L.O.I 0.40

The screen analysis of this coarse spodumene, not calcined, which may be considered to be to 140 mesh, is typically as follows, nominally mesh:

Mesh: Percent +20 0.0

Coarse spodumene calcined at 450 to 500 C. and converted at least partially into {i spodumene, has a typical screen analysis as follows when in nominal size of 20 to 140 mesh, called 20 mesh:

Mesh: Percent FINE LITHIUM MINERAL Fine lithium mineral having at least and preferably at least through 200 mesh and nominally called 200 mesh, is also used in the present invention. A typical chemical analysis for 200 mesh spodumene is as follows:

Chemical: Percent Li O 7.1 F6203 Na O 0.25 K 0 0.35 A1 0 24.4 SiO 65.5 CaO+MgO 0.70 (111,0 0.001 L.O.I 0.5

A typical screen analysis for the fine lithium mineral is as follows:

Mesh: Percent +20 0.0 0.3 1.0 +200 5.3 -200 93.5

The petalite and spodumene are on sale by Foote Mineral Company.

CLAY

Any suitable ball clay may be used, a suitable form being Hanover clay from United Clay Mines. The ball clay should be finely divided, almost entirely through 200 mesh.

The fireclay used should be finely divided, almost entirely through 100 mesh. A suitable fireclay is that supplied by A. P. Green Refractories Company.

The fireclay has the following screen analysis:

Loss on ignition A suitable kaolin for use in making whiteware is EPK supplied by United Clay Mines. It is substantially entirely through 200 mesh.

STONEWARE In making stoneware according to the invention the composition used is as follows:

Wider range Coarse petalite Coarse spodumene Fine petalite or spodumene--." Ball clay Fireclay with petalite only and quantity of fine lithium mineral exceeds quantity of coarse lithium mineral Fireclay with petalite only and quantity of coarse lithium mineral exceeds quantity of fine lithium mineral Fireclay with spodumene In making up the stoneware the dry powdered ingredients are mixed in the correct proportions, having previously been graded so that they are of the proper par ticle size. Any suitable ceramic mixer may be used. After mixing to obtain a uniform composition, the mix is moistened until it becomes plastic. In the typical case between 20% and 50% of the weight of the dry ingredients will be added to make the, mix workable. The examples in the present case were produced using 20% of water on the dry ingredients.

After mixing, the plastic mix is formed into articles, using any suitable technique, for example a wheel, press, extruder, or otherwise. The formed shapes are then dried, for example at room temperature and then in a suitable drier for example at 250"; F. for an adequate time, depending on the size of the articles. When completely dried the shapes are fired in a ceramic kiln at a temperature of cones 8-10 inclusive.

When completely dried the shapes are fired in a ceramic kiln at a temperature of 1236 to'1285 C. inclusive (cones 8-10). I find it desirable toraise the temperature on the objects to be fired, when they are of the order of three or four inches in diameter and one quarter inch thick, at a rate of 165 C. per hour from room temperature.

The fired shapes if they are to be glazed are then coated with a suitable glaze as set forth below. It is found that the color of the glaze is warmer than in the case of prior art stoneware.

WHII EWAREg (PORCELAIN) In making whiteware of porcelain according to the invention the following composition will be employed:

Percent Preferred Wider range Component Coarse petalite or I Coarse spodumeneuul Fine petalite or spodume Kaolin Ball clay (optional) 1 Up to 35%. 1 Up to 30%.

The whiteware; may be produced by the same techproperties of avoiding fracture by thermal shock and 6 brightening the colors of a glaze. It will be fired in the range of 1236 to 1285 C. inclusive (cones 8-10). I find it desirable when the objects are about three inches in di ameter and one quarter inch thick to raise the temperature 150 C. per hour from room temperature.

EXAMPLES A Examples A show the results of 24 tests made on vari ous compositions of coarse petalite nominally through 20 mesh (uncalcined), fine petalite nominally through 200 mesh (uncalcined), ball clay and fireclay. The compositions are shown in Table 1. In this table and in the others, in reporting results where no crack or fracture was noted under the 3000" F. oxyacetylene flame pinpointed at the center of the test ceramic disc, an asterisk is used. Where fracture occurred in this test the word no is employed.

It will be observed that Table I shows satisfactory results in experiments l-lO, doubtful results in experiments 11 and 12 and unsatisfactory results in experiments l3-24.

Table 2 lists the ultimate analysis of the composition employed in test 1 of Table 1, it being noted that the ultimate analysis for each component of ball clay was multiplied by 20% since 20% of ball clay was used; the ultimate analysis for each componet of fireclay was multiplied by 20% since 20% of fireclay was used; the ultimate analysis for 20 mesh petalite was multiplied by 10% since 10% of 20 mesh petalite was employed, and the ultimate analysis for 200 mesh petalite was multiplied by 50% since 50% of this material was employed. The totals show the analysis of the stoneware.

Table 3 is similar to Table 2, but shows the analysis for the composition used in test 5 of Table 1.

All of the specimens in Examples A and in all other examples were fired between cones 8 and 10 inclusive.

EXAMPLES B Table 4 shows a series of eight experiments made with different compositions of 20 mesh petalite (uncalcined),

.with 200 mesh spodumene (uncalcined), ball clay and fireclay. All gave successful results under the fire exposure test. Table 5 shows the ultimate analysis for the composition in test 1 of Table 4.

EXAMPLES C r in Table 6.

EXAMPLES D Table 8 shows a series of tests made on 30 mesh spoduball clay and fireclay. The results as shown were all good in the flame test. Table 9 shows the ultimate analysis of the composition used in test 4 of Table 8.

EXAMPLES E Table 10 shows a series of test results obtained for various compositions of 20 mesh spodumene calcined at a tempertaure of 450 to 500 C., 200 mesh petalite (uncalcined), ball clay and fireclay. All of the results were successful in the flame test.

EXAMPLES F ball clay and fireclay. The results as shown were all successful in the flame test.

mmmm

Petallte 20 mash m c H a B Test Series Pg? Test Series TgS Test number..

PORCELAIN) Test series whiteware .'IHERMAL SHOCK CLAY (WHITEWARE TABLE 10.THERMAL SHOCK CLAY (STONEWARE) TABLE IIr- IHERMAL SHOCK CLAY (STONEWARET TABLE 12 CaO MgO K10 N520 L110 Calclned spodumene 20 mesh. 45 SpodumeneZOOmesh Ballclay Fireclay-. Rmnlfz CaO MgO K10 NazO LiaO Testnumben...

BallClay Results C80 MgO K20 N820 Lizo 8 "25 Test number.

CBO MgO K10 N820 L120 TiO:

Analysis of Test 5, Table 1 TABLE 3 TABLE A1101 FeaOa.

TABLE 7 SiO: A110: F610! TABLE 9 S: A1201 F620! Bio:

Tast Series as.

Flreclay.

Test Series 8.1.

Test number...--

Test Series 8.3.

30 mesh .Total Total TABLE 4.-THERMAL SHOCK CLAY (STONEWARE) TABLE B.THERMAL SHOCK CLAY (STONEWARE) Spodumene 30mesh..--... Petallte 200mesh.....

Total- TABLE 8.-THEBMAL SHOCK CLAY (STONEWARE) T0tal- Analysis of Test 1, Table 5 Petalita mesh Analysis of Test 2, Table 6....-

Spodumene mesh.

Petalite 200 mesh Analysis of Test 4, Table 8-.

Petallte 20 mesh Test number- Petallte 20 mesh- Spodumene 200 mesh--- Ball clay Spodmnene 200 mes Ball clay- Test number Bpodumene Spodumene 30 mesh Spodumene 200 mes Ball clay.

Fireclay....

TABLE 13 v v I Analysis of Test 6, Table 12 SiOz AHOF'FezOr TiOz C80 7 v 'KrO' NazO- -Ll1O---- Petalite 20 mesh 7. 75 1. 60 e 03 04 .42 Petalite 200 mesh 23.25 4.80 .09 .12 20 Kaolin 11.20 9. 70- 1 .4- 1-02 .05 .05 3.05 Ball clay 17.30 10. 50 2 .5 .07 430 1.00

Total 59 50 26.60 3 9 .09 .09 .35 1.21' '4.73

Having thus described my invention what I claim as Astonewa're composition of claim 1, comprising 25 1. A thermal shock resistant clay stoneware composition, essentially consisting of a relatively coarse lithium mineral consisting of 825% of petalite or'7 25% ofspodumene, said coarse petalite-being more specifically a material considered to be a 20 mesh product and'said coarse spodumene being more specifically a material considered to be a 20 +140 mesh product and in the case of both the coarse petalite and the coarse spodumene the coarse lithium mineral having as a particular part of its characteristics at least 65% through 20 and on 200 mesh, a relatively fine lithium mineral consisting of 1050% of petalite or spodumene, said fine lithium mineral having at least 80% through 200 mesh, 20-40% of ball clay, an fireclay in the following proportions:

Percent when only petalite is employed, and the quality of fine lithium mineral exceeds the quantity of coarse lithium mineral 20-30 when only petalite is employed and the quantity of coarse lithium mineral exceeds the quantity of fine lithium mineral 20-33 when spodumene is employed as at least one of the compounds 20 32 said composition producing a product which will withstand a localized flame having a temperature of at least 3000 F. without cracking either in heating or in cooling- 4. A stoneware composition of claim 1, comprising 35% of ball clay. 5. Astoneware c'ompositionof'claim- 1r,--compfi'sing-2-5- of fireclay.

- Reerence. i!d.,.

UNITED STATES PATENTNS 2,260,000 10/1941 Burgess et a1 106-9145 3,279,930,10/1966 Van der Beck et al. 106-69 '3,097,101 #1963 Lester... 106? .YOTI- IER REFERENCES Searle, A. B.: Refractory Materials; London, 1924, pp.

Smoke, E. 1.; Ceramic Composi tionsl .QI Qi near Tiier- ALLEN B. CURT'IS, Primary Examiner MIL BELL,- Assistant Examiner "its. oi. XR. 

